A standard method of plating metallic strip is to move the strip through plating bathes having a high concentration of metal ions in solution. An electrical potential is maintained between the strip and the bath causing an electro-chemical reaction to take place. Metallic ions in the bath combine with electrons to form a metallic layer on the surface of the strip. Zinc plating or galvanizing of steel for rustproofing the steel is an example of metallic strip plating accomplished in this manner.
The processing steps for electro-plating strip metal are well known. A coil of metallic strip is unwound and attached to the trailing end of a preceding coil at a welding station. From this station, the strip moves through preparation stations where typically the surface of the strip is cleaned and acid treated to prepare it for plating. The drive rollers then feed the strip over a contact roll that energizes the strip as it is fed into a plating bath in a cell. As the strip exits the cell it passes over another contact roll. Usually a strip plating line will have a series of such cells through which the strip is sequentially fed. The plating is performed under controlled conditions wherein typically the thickness of the plating is monitored and plating current and line speed are adjusted to produce a desired plating thickness. The plated strip is then washed, dried and recoiled for shipment.
Since efficient plating requires high levels of electric energy and that energy is fed through rotating contact rolls in the harsh environment of a plating line, the provision of suitable commutation for delivering energy to contact rolls has been a persistant problem. A myriad of constructions have been tried and used but all have shortcomings. Typically a rotating contact roll is supported by a shaft that is journalled for rotation in support bearings. Electrical energy is applied to the shaft by a commutator, typically including a brush and slip ring. Two patents illustrative of this approach contact roll energization design are U.S. Pat. No. 3,678,226 to Hatagi et al. and U.S. Pat. No. 3,839,606 to Paradine. Experience with these prior art designs has shown that the bearings and commutators typically form the weakest part of the contact roll arrangement and most frequently require adjustment, maintenance, and replacement.